It is well known to a person skilled in the art that certain motor fuels or liquid hydrocarbon-containing fuels stored in the presence of air for long periods of time are subject to the formation of solid deposits, in particular at low temperature. These problems of deposits are connected with the presence of unstable molecules contained in the motor fuels or liquid hydrocarbon-containing fuels. These unstable molecules oxidize easily in the presence of oxygen, in particular in the light, under the effect of ultraviolet (UV) radiation, and/or in the presence of traces of metals, which catalyse the oxidation reaction and therefore promote the formation of deposits. The unstable molecules which are sensitive to oxidation are mainly molecules containing unsaturations, for example olefins in gasolines, fatty acid methyl or ethyl esters (FAME and FAEE), esters of animal fats or other sources of triglycerides in biodiesels or olefins and partially hydrogenated aromatics in the cuts of distillates originating from catalytic or thermal cracking of products originating from petroleum refining.
The deposits that accumulate on the filters cause obstruction of the filters. A great many additives used for reducing the formation of deposits have been described extensively in the literature. Among the solutions proposed, the use of conventional antioxidants such as the phenolic or amine antioxidants has been proposed. By way of illustration, application US2010/0075876 may be mentioned, which proposes a composition comprising at least one cyclic amine antioxidant, for example diphenylamine and a phenolic antioxidant, 2,6-di-tert-butyl-4-methylphenol (BHT).
The technical problem that the invention aims to solve is to improve the oxidation and/or storage stability of compositions of motor fuels or liquid hydrocarbon-containing fuels. The present invention aims in particular to stabilize a biodiesel of type B100 in order to obtain a value of Rancimat induction time (Tind) according to standard EN 15751 greater than or equal to 8 hours. A particular aim of the invention is to obtain a gain in the induction time value (ΔTind) greater than or equal to 2.
The alkylphenol-aldehyde resins originating from the condensation of alkylphenol and aldehyde have long been known as flow improvers for mineral oils: see for example EP 311 452, which describes products of condensation of at least 80 mol % of dialkylphenols and aldehydes having from 1 to 30 carbon atoms; EP 857 776, which describes the use of alkylphenol-aldehyde resins in which the alkyl groups of the alkylphenol have from 4 to 12 carbon atoms and the aldehyde from 1 to 4 carbon atoms and not containing more than 10 mol % of alkylphenols having more than one alkyl group, in combination with ethylene/vinyl ester copolymers or terpolymers for improving the fluidity of mineral oils; EP1 584 673, which describes alkylphenol-aldehyde resins with Mn between 1000 and 3000 originating from the condensation of a C1-C4 aldehyde and a mixture of alkylphenols, predominantly monoalkylphenol, the alkyl group having from 1 to 20 carbon atoms, intended for improving the low-temperature flow properties of motor fuel compositions. Modified alkylphenol-aldehyde resins have also been proposed as additives for improving the low-temperature flow of mineral oils: EP 1 767 610 describes alkylphenol resins the condensation reaction of which with the aldehydes is carried out in the presence of fatty acids having from 2 to 50 carbon atoms, or derivatives thereof, such as esters. In patent application WO2012/085865 and more recently in application FR2012/55755, the applicant proposed novel modified alkylphenol-aldehyde resins, usable for improving the lowtemperature stability of motor fuels and liquid hydrocarbon-containing fuels.
Continuing this research, the applicant discovered a novel use of these modified alkylphenol-aldehyde resins in compositions of motor fuels or liquid hydrocarbon-containing fuels. In particular, the present invention relates to the use of at least one modified alkylphenol-aldehyde resin as additive for improving the oxidation and/or storage stability of a motor fuel or liquid hydrocarbon-containing fuel composition, said modified alkylphenol-aldehyde resin can be obtained by Mannich reaction of an alkylphenol-aldehyde condensation resin                with at least one aldehyde and/or one ketone having from 1 to 8 carbon atoms, preferably from 1 to 4 carbon atoms;        and at least one hydrocarbon-containing compound having at least one alkylmonoamine or alkylpolyamine (alkylamine) group, having between 1 and 30 carbon atoms, preferably between 4 and 30 carbon atoms, said alkylphenol-aldehyde condensation resin itself can be obtained by condensation        of at least one alkylphenol substituted with at least one linear or branched alkyl group having from 1 to 30 carbon atoms, preferably a monoalkylphenol,        with at least one aldehyde and/or one ketone having from 1 to 8 carbon atoms, preferably from 1 to 4 carbon atoms.        
According to a particular embodiment, said use makes it possible to improve the storage stability of the motor fuel or liquid hydrocarbon-containing fuel composition at a temperature less than 0° C., preferably less than −5° C., more preferably less than or equal to −10° C. According to another particular embodiment, this use makes it possible to reduce the quantity of deposits formed during the storage of the motor fuel or liquid hydrocarbon-containing fuel composition. According to another preferred particular embodiment, the modified alkylphenol-aldehyde resin can be obtained from at least one alkylphenol substituted in the para position, preferably starting from p-nonylphenol.
According to another preferred particular embodiment, the modified alkylphenol-aldehyde resin can be obtained from at least one aldehyde and/or one ketone selected from formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde, 2-ethylhexanal, benzaldehyde, acetone, and preferably from at least formaldehyde. According to one variant, the modified alkylphenol-aldehyde resin can be obtained from at least one alkylamine having at least one primary amine group, and advantageously at least one compound in which all the amine groups are primary amines. According to another variant, the modified alkylphenol-aldehyde resin can be obtained from p-nonylphenol, formaldehyde and at least one hydrocarbon-containing compound having at least one alkylmonoamine or alkylpolyamine group.
According to another preferred particular embodiment, the modified alkylphenol-aldehyde resin can be obtained from at least one fatty-chain alkylamine or from a mixture of fatty-chain alkylamines, and preferably from alkylamine(s) having a number of carbon atoms between 12 and 24, preferably between 12 and 22. According to one variant, the modified alkylphenol-aldehyde resin has a viscosity at 50° C. measured using a dynamic rheometer at a shearing rate of 100 s−1 on a solution of said resin diluted with 30% by weight of an aromatic solvent comprised between 1000 and 10000 mPa·s, preferably between 1500 and 6000 mPa·s and advantageously between 2500 and 5000 mPa·s.
According to certain particular embodiments, the object of the invention also has one or more features listed below:                the modified alkylphenol-aldehyde resin is used as an additive in a form diluted in a solvent, preferably aromatic.        the modified alkylphenol-aldehyde resin is used in the motor fuel or liquid hydrocarbon-containing fuel composition in combination with one or more additional additives.        the additional additives are selected from dispersants/detergents, carrier oils, metal deactivators, metallic passivators, antioxidants, dyes, antistatic additives, corrosion inhibitors, biocides, markers, thermal stabilizers, emulsifiers, friction reducing agents, surfactants, cetane improvers, anti-clouding agents, additives improving the conductivity, reodorants, lubricity additives, lubricants and mixtures thereof.        a quantity of modified alkylphenol-aldehyde resin comprised between 5 and 5000 ppmw, preferably between 10 and 2000 ppm, more preferably between 50 and 1200 ppm, even more preferably between 50 and 600 ppm, is added to the motor fuel or liquid hydrocarbon-containing fuel composition.        the motor fuel or liquid hydrocarbon-containing fuel composition comprises a motor fuel or liquid hydrocarbon-containing fuel selected from gas oils, diesel fuels, gasolines, biofuels, jet fuels, domestic fuel oils (DFO) and heavy fuel oils.        the motor fuel or liquid hydrocarbon-containing fuel composition comprises a motor fuel or other fuel selected from the middle distillates with a boiling point temperature comprised between 100 and 500° C., preferably 140 to 400° C.        the motor fuel or liquid hydrocarbon-containing fuel composition comprises vegetable and/or animal oils and/or esters thereof and/or biodiesels of animal and/or vegetable origin, preferably the esters are fatty acid methyl esters (FAME) or fatty acid ethyl esters (FAEE), in particular vegetable oil methyl esters (VOME) or vegetable oil ethyl esters (VOEE).        the motor fuel or liquid hydrocarbon-containing fuel composition is a biodiesel of type B100, whose value of induction time (Tind) obtained by a Rancimat test according to standard EN 15751 is greater than or equal to 8 hours, advantageously a gain in value of induction time (ΔTind) obtained by the Rancimat test according to standard EN 15751 is greater than or equal to 2.        